igneous

Granodiorite (Gneissic texture)

Granodiorite (containing Quartz SiO2, Plagioclase Feldspar, and Biotite)

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (gray, white, black); Luster: Dull to vitreous; Crystal structure: Phaneritic/Medium-grained; Cleavage: Poor; Specific gravity: 2.6-2.7

Hardness: 6-7 (Mohs scale)
Color: Salt and pepper (gray, white, black)
Luster: Dull to vitreous

Identified April 10, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (gray, white, black); Luster: Dull to vitreous; Crystal structure: Phaneritic/Medium-grained; Cleavage: Poor; Specific gravity: 2.6-2.7

Formation & geological history

Formed from the slow cooling of silica-rich magma below the Earth's surface. This specimen appears to have mild metamorphic alignment (gneissic character), suggesting it was subjected to heat and pressure after its initial igneous formation.

Uses & applications

Used primarily in heavy construction, road base, and as decorative dimension stone (frequently sold as 'granite' in the countertop industry).

Geological facts

Granodiorite is the rock that makes up the famous Rosetta Stone. It is the intermediate rock between granite and diorite, containing more plagioclase than orthoclase feldspar.

Field identification & locations

Identify by its 'salt and pepper' appearance and hardness (it will scratch glass). Look for the presence of translucent quartz crystals nestled between opaque white feldspars and black mica flakes. Commonly found in large batholiths like the Sierra Nevada mountains.

Other igneous specimens

See all

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral